Re: [gentoo-dev] RFC: sed script redundancy

[Fabian Groffen <grobian@gentoo.org>]

On 21-05-2011 19:34:34 +0200, Jeroen Roovers wrote:
> On Fri, 20 May 2011 17:56:00 +0200
> Fabian Groffen <grobian@gentoo.org> wrote:
> 
> >   sed -e "<pattern>" "${file}" | diff "${file}" -
> > 
> > followed by the actual sed -i -e ...
> > 
> > This way I didn't need to write an intermediate file.
> 
> The problem there is that sed might be called just once on any one file,
> but in the tree it is often invoked with multiple scripts, so this
> simple implementation lacks a way to evaluate which sed scripts are
> useful.
> 
> Also, how do I ensure the sed replacement works only on invocations
> inside the ebuild, and not, say, in portage's internals?

(not tested, but as proof of concept)

alias sed my_sed
my_sed() {
	local oargs="${@}"
	local arg
	local nargs=()
	local hadi=
	local hade=
	while [[ -n $1 ]] ; do
		case "$1" in
			-i)
				# ignore this flag
				hadi=yes
				;;
			-e|-f)
				shift
				nargs+=( "-e$1" )
				hade=yes
				;;
			-*)
				nargs+=( "$1" )
				hade=yes
				;;
			*)
				if [[ -z ${hade} ]] ; then
					nargs+=( "$1" )
				elif [[ -z ${hadi} ]] ; then
					# there is no inline replacing, not much we can do
					break
				else
					sed "${nargs[@]}" "$1" | diff -q "$1" - > /dev/null \
						&& ewarn "sed ${oargs} has no effect on $1" 
				fi
				;;
		esac
		shift
	done

	\sed "${oargs}"
}


-- 
Fabian Groffen
Gentoo on a different level